In international studies, the incidence of cervical squamous cell carcinoma has been found to decrease, whereas no changes or even increases were observed in the incidence of cervical adenocarcinoma. It has been suggested that the current screening practices are not sufficient to detect adenocarcinoma precursor lesions. We investigated whether incidence rates of squamous cell carcinoma and adenocarcinoma differ between screen-detected and clinically detected cancers in the Netherlands.
All cervical cancer cases diagnosed between 1997 and 2007 were included using data from the Dutch nationwide registry of histo- and cytopathology (PALGA) and the Netherlands Cancer Registry. Analyses were restricted to cancers in women aged 29-64 years old, being the ages of the screening program in the Netherlands. Trends in the incidence rates of squamous cell carcinoma and adenocarcinoma were evaluated by calculating the estimated annual percentage change (EAPC). To compare the two sets of trend data, we used a test of parallelism (Joinpoint Trend Analysis).
Overall, screen-detected cancers comprised of 75% squamous cell carcinomas, 17% adenocarcinomas and 8% of other histological types, which was similar to clinically detected cancers (75%, 20% and 6%, respectively; p=0.771). In the period 1997-2007, both screen-detected squamous cell and adenocarcinoma increased (EAPC = 8.5, 95% CI: 1.4, 16.0; and EAPC = 14.2, 95% CI: 5.2, 23.8, respectively; p=0.014). Clinically detected cancers initially increased during 1997-2002 (EAPC = 26.6, 95% CI: 6.4, 50.0), yet showed a (non-significant) decreasing trend during 2002-2007 (EAPC = -2.4, 95% CI:-12.5, 8.9), a pattern similar to squamous cell and adenocarcinoma (p=0.648).
Overall, the distribution of cervical squamous cell and adenocarcinoma is similar in screen-detected and clinically detected cancers. The trends in the incidence rates of screen-detected and clinically detected cases were similar for both cancer types. The results suggest that the current screening practice in the Netherlands equally detects squamous cell and adenocarcinoma .